GE6252-Basic Electrical and Electronics Engineering.pdf
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Transcript of GE6252-Basic Electrical and Electronics Engineering.pdf
VETRI VINAYAHA COLLEGE OF ENGINEERING AND TECHNOLOGY THOTTIAM, TRICHY -621 215
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
Subjectname: GE6252 - Basic Electrical and Electronics Engineering Year / Departmetn/Semester : I / Common to Mechanical and Civil Engineering / II Staff Name : Mr.B.Prasanth ., M.E Assistant Professor EEE
UNIT I
ELECTRICAL CIRCUITS AND MEASUREMENTS
1. What is charge and current ?
The charge is an electrical property of the atom particles of which matter
consists. The unit of charge is coulomb.
The flow of free electron in a metal is called electric current. The unit current is
ampere. Current (I) = Q / t
2. Define Voltage and Power.
The potential difference between two points in an electric circuit called voltage.
The unit of voltage is the volt. Voltage represented by V or v. The rate of doing work by electrical energy or energy supplied per unit time is
called the power. Its unit is watts P = VI; P = I
2R; P = E
2 / R. P = Energy / time = W/t
3. Under what condition AC circuit said to be resonant?
If the inductive reactance of the circuit is equal to capacitive reactance then the
circuit is said to be resonance. XL=XC
4.Define resistance. Resistance is the property of a substance, which opposes the flow of electric
current. Also it can be considered as electric friction. Whenever current flows through a resistor, a voltage drop occurs in it and it is dissipated in the form of
heat. Unit of resistance is ohm. Symbol is measured with a help of ohmmeter.
5. Define international ohm.
International ohm is defined as the resistance offered to the flow of current by a
column of mercury of length 106.3cm; 14.452gm in mass with uniform cross
section at 0oC.
6.What are the factors affecting resistance?
(i) Length (ii)Area of cross section
Nature and property of the material
Conductance and conductivity
7. What is meant by electrical energy? Energy is the total amount of work done and hence is the product of power and
time. W = Pt = EIt = I2Rt = E
2 / Rt Joules (watt –second)
8. Write down the expression for effective resistance when three resistances are connected
in series and parallel. For series connection (for three resistors) R= R1 + R2 + R3
For parallel connection (for two resistors) R = R1 R2 /(R1 + R2)
9. State Kirchhoff’s laws
Kirchhoff’s current law
The sum of currents flowing towards the junction is equal to the sum of the
currents flowing away from it.
Kirchhoff’s voltage law
In a closed circuit, the sum of the potential drops is equal to the sum of the
potential rises.
10. What is series circuit?
When the resistors connected in a circuit such that the current flowing through
them is same is called as series circuit. 11. What is parallel circuit?
When resistors are connected across one another so that same voltage applied to
each, then they are said to be in parallel the circuit is called as parallel circuit. 12. State Ohm’s law.
When t e m p e r a t u r e remains constant, current flowing through a circuit is directly proportional to potential deference across the conductor. V= I*R(Volts)
13. Define form factor. Form factor = RMS value / Average value
14. Define crest (peak) factor. Crest (peak) factor = Maximum value / RMS value
15. Define apparent power. The maximum power consumed by the circuit is called apparent power. The unit
VA. S = VI.
16. Define RMS value It is the mean of the squares of the instantaneous value of current over one
complete cycle. 17. Define capacitance.
A capacitor is a circuit element that, like the inductor, stores energy during periods of time and return the energy during others. In the capacitor, storage takes place in an electric field unlike the inductance where storage is magnetic field. Two parallel plates separated by an insulating medium form a capacitor. The emf across the capacitor is proportional to the charge in it i.e q or e = q/C, Where, C is constant called capacitance.
PART- B
1. (i) State and explain Kirchoff’s law. (8)
(ii) Explain the working of a Dynamometer wattmeter with a neat sketch. (8)
2. (i) Explain any one type of MI instruments. (8)
(ii) Explain the working principle of PMMC instruments. (8)
3. Explain the construction and principle of operation of single phase energy meter. (16)
4. (i) A series circuit has R=10_, L=50mH, and C=100μF and is supplied with 200V,50Hz.
Find (i) Impedance (ii) current (iii) power (iv) power factor (v) voltage drop across the
each element. (8)
(ii)Derive the equation for equivalent resistance of number of resistors connected in
parallel. (8)
5. A 400V is applied to three star connected identical impedances each consisting of a
40 _ resistance in series with 3_ inductance reactance. Find (i) line current (ii) Total
power supplied. (16)
6. Find the current through each branch by network reduction technique. (16)
7. Calculate a) the equivalent resistances across the terminals of the supply, b) total current
supplied by the source and c) power delivered to 16 ohm resistor in the circuit shown in
figure. (16)
8. In the circuit shown, determine the current through the 2 ohm resistor and the total
current delivered by the battery. Use Kirchhoff’s laws. (16)
9. (i) In the network shown below, find the current delivered by the battery. (10)
(ii) Discuss about voltage and current division principles. (6)
Unit – II
Electrical Machines
1. What is an electric generator?
An electrical machine, which converts mechanical energy into electrical Energy,
is called as electric generator.
2. What is an electric motor?
An electrical machine, which converts electrical energy into mechanical Energy,
is called as electric motor.
3. What is meant by magnetic flux?
The magnetic lines of force existing around a magnet is called magnetic
flux. It’s unit is Weber. 1wb=10 8
magnetic flux lines
4. State faraday’s law of electromagnetic induction.
Whenever a conductor cuts the magnetic lines of force an emf is induced in
it.
5. What is the use of commutator?
A device is used in a dc generator to convert the alternating emf into unidirectional emf is called commutator.
6. What is the function yoke?
It serves the purpose of outermost cover of the dc machine. So that the
insulating material gets protected from harmful atmospheric elements like
moisture, dust and various gases like SO2, acidic fumes etc. It provides
mechanical support to the poles.
7. What is the choice of material for the following?
1. Yoke 2 . pole 3.Field winding 4.Armature winding
1. Yoke: It is prepared by using cast iron because it is cheapest.
2. Pole: It is made up of cast iron or cast steel.
3. Field winding:It is made up of aluminium or copper.
4. Armature winding:It is made up of cast iron or cast steel.
8. Give the emf equation of dc generator. E= ZNP/60A where E⇒ Generated emf in volts ⇒Flux produced
per pole in Weber
Z⇒Total no. of conductors
N⇒Speed of armature in rpm E= ZN/60for lap winding
A=P E= ZNP/120 for wave winding A=2
9. What are all the two types of
excitation?
Separate excitation
When the field winding is supplied from external, separate dc supply i.e. Excitation of field winding is separate then the generator is called separately excited generator.
Self excitation When the field winding is supplied from the armature of the generator itself then it
is called as self-excitation.
10. What is meant by residual magnetism?
Practically though the generator is not working, without any current through field winding, the field poles posses some magnetic flux. This is called as residual magnetism.
11. State that the Fleming’s left hand rule.
The rules states that outstretch the three fingers of the left hand namely the first finger, middle finger and thumb such that they are mutually perpendicular to each other. Now point the first finger in the direction of magnetic field and the middle finger in the direction of the current then the thumb gives the direction of the force experienced by the conductor.
12.What is Lenz’s law? Lenz’s law states the direction of induced emf is always so as to oppose the
cause producing it
13. List the different types of DC motor. DC series motor DC Shunt motor DC Compound motor
Long shunt compound motor
Short shunt compound motor
14. What is the necessity of starter?
To restrict high starting armature current, a variable resistance is connected in series with the e armature at start. This resistance is called starter.
15. What are all the factors affecting the speed of a DC motor? The flux The voltage
across the
armature The
applied voltage
16.What is meant by Swinburne’s test? Without actually loading the motor the losses and hence efficiency at
different loads can be found out.
17. List out the applications of various types of generators.
Separately excited generator
As a separate supply is required to excite the field, the use is restricted to some special applications like electroplating, electro refining of materials etc
Shunt generator
Commonly used in battery charging and ordinary lighting purposes.
Series Generators Commonly used as boosters on dc feeders, as a constant current generators for welding
generator and arc lamps.
Cumulatively compound generators These are used for domestic lighting purposes and to transmit energy over long distance.
Differential compound generator The use of this type of generators is very
PART B 1. Explain the construction and principle of operation of a DC generator with neat sketch. (16)
2. (i) Derive the equation for induced EMF of a DC machine. (8)
(ii) Derive the torque equation of DC motor. (8)
3. Describe the construction details of transformer and also explain the principle of
operation. (16)
4. (i) Derive the EMF equation of a transformer. (8)
(ii) Explain the principle of operation of DC Motor. (8)
5. Explain the construction and principle of operation of single phase induction motor. (16)
6. A transformer with 40 turns on the high voltage winding is used to step down the voltage
from 240V to 120V. Find the number of turns in the low voltage winding. (16)
7. A 4 pole, wave wound generator having 40 slots and 10 conductors placed per slot. The
flux per pole is 0.02 wb. Calculate the generated emf when the generator is drive at 1200
rpm. (16)
8. A 25kw, 250V, dc shunt generator has armature and field resistances of 0.06ohm and
100ohm respectively. Determine the total armature power developed when working (1) as a
generator delivering 25 kw output and (2) as a motor taking 25kw. (16)
UNIT III
SEMICONDUCTOR DEVICES AND APPLICATIONS
PART A
1. Define Transistor.
Transistor consists of two junctions formed by sandwitching either P- type or N-type
semiconductor between a pair of opposite types.
2. Write the current amplification factor for a CB transistor.
Change in Collector Current / at constant VCB Change in emitter current
3. Write the current amplification factor for a CE transistor.
Change in Collector Current /Change in base current at constant VCE
4. Define transistor action.
A transistor consists of 2 coupled PN junctions. The base is a common region to both
junctions and makes a coupling between them. Since the base regions are smaller, a
significant interaction between junctions will be available. This is called transistor
actions.
5. Define rise time
It is the time required for the current to rise from 0 to 90 percentage of the maximum
value.
6. Define turn-on time
It is the time required for the current to rise from 0 to 90 percentage of the maximum
value ton = td + tr
7. Define fall time
It is the time required for the Collector current to fall from 90 to 10 percentage of Ics.
8. Define turn-off time
It is the time required to fall from 100 to 90 percent of Ics. Toff=ts+tr
9. Define hybrid parameters.
Any linear circuit having input and output terminals can be analysed by four
parameters(one measured on ohm, one in mho and two dimensionless) called hybrid or
h-parameters.
10. What are the use of h - Parameters?
It perfectly isolates the input and output circuits.
Its source and load currents are taken into account.
11. What are the advantages of transistors?
Low operating voltage.
Higher efficiency.
Small size and ruggedness
12. What are the types of transistors?
Unipolar junction transistor Bipolar junction transistor.
13. What is mean by characteristics of transistor? The interrelation of the various currents and voltages can be plotted
graphically which are commonly known as the characteristics of transistor. 14. What are the types of BJT?
n-p-n Type
p-n-p Type.
PART B
1. Explain intrinsic and extrinsic semiconductors with neat diagrams. (16)
2. Describe the working of a PN junction diode with neat diagrams. Also explain its V-I
characteristics. (16)
3. What is a Zener diode? Explain the operation of Zener diode and draw its characteristics.
(16)
4. Explain the operation of half wave rectifier with neat sketch and derive the necessary
expression. (16)
5. Explain the operation of centre tapped full wave rectifier with neat diagram. (16)
6. Explain with a neat diagram how the input and output characteristics of a CE
configuration can be obtained. (16)
UNIT IV
DIGITAL ELECTRONICS
1. Define binary logic? Binary logic consists of binary variables and logical operations. The variables are
designated by the alphabets such as A, B, C, x, y, z, etc., with each variable having only two distinct values: 1 and 0. There are three basic logic operations: AND, OR, and NOT.
2. Convert (634) 8 to binary 6 3 4
110 011 100 Ans = 110011100
3. Convert (9B2 - 1A) H to its decimal equivalent.
N = 9 x 16 2
+ B x 16 1
+ 2 x 16 0
+ 1 x 16 -1
+ A (10) x 16 -2
2304 76 + 2 + 0.0625 + 0.039
Ans= 2482.1 10
4. State the different classification of binary codes? Weighted codes
Non - weighted codes
Reflective codes Sequential codes
Alphanumeric codes
Error Detecting and correcting codes.
5. Convert 0.640625 decimal number to its octal equivalent.
0.640625 x 8 = 5.125
0.125 8 = 1.0
Ans =0.640 625 10 = (0.51) 8
6. Convert 0.1289062 decimal number to its hex equivalent
0.1289062 x 16 = 2.0625
0.0625 x 16 = 1.0
Ans= 0.21 16
7. State the steps involved in Gray to binary conversion?
The MSB of the binary number is the same as the MSB of the gray code number. So write it down. To obtain the next binary digit, perform an exclusive OR operation between the bit just written down and the next gray code bit. Write down the result.
8. Convert gray code 101011 into its binary equivalent.
Gray Code: 1 0 1 0 1 1
Binary Code: 1 1 0 0 1 0
9. Substract (0 1 0 1) 2 from (1 0 1 1) 2
1 0 1 0
0 1 0 1
Answer = 0 1 1 0
10. Add (1 0 1 0) 2 and (0 0 1 1) 2 (APR 2005)
1 0 1 0
0 0 1 1
Answer = (1 1 0 1) 2
11. Using 10’s complement subtract 72532 - 3250
M =72532 10’s complement of N = + 96750 Sum = 169282
Discard end carry
Answer = 69282
12. Convert the given expression in canonical SOP form Y = AC + AB + BC
Y = AC + AB + BC
=AC (B + B’) + AB(C + C' ) + (A + A')BC
=ABC + ABC' + AB'C + AB'C' + ABC + ABC' + ABC
=ABC + ABC' +AB'C + AB'C' [A + A =1]
PART B
1. Describe in detail about D- flip flop , T- flip flop and JK- flip flop (16)
2. i. Explain the operation of 4-bit synchronous UP counter with a neat diagram (12)
ii.Express the function XOR gate using NAND gates. (4) 3. Write short notes on (1)J-K Flip flop (2) R-S Flip flop (3) D flip flop (4).Toggle Flip flop
(16)
4. i. Express the given function with three AND gates and one OR gate
A’BC + AB’C + ABC’ + ABC (10)
ii. Explain the operation of half adder with neat diagram (6)
5. i. Draw the logic diagram of clocked Master – slave JK flip flop and explain its working
(8)
ii. Describe the operation performed by the following arithmetic circuits
a. Full adder b. Half adder (4+4)
6. i. Apply Boolean laws and Simplify the following Boolean expression a. XY + X’Z + YZ b. ( A’+B+C’).( A+B+C). (C+D) (8)
ii. Explain the working of JK- flip flop with its logic diagram (8)
6. Discuss the working principle of D/A and A/D converters (16)
7. With necessary diagrams explain the function of any one type of ADC and DAC (16)
8. i. Explain the operation of successive approximation type ADC with a neat sketch
(8)
ii.Draw the circuit of Binary weighted resistor Digital to analog Converter and Explain its
operation 9. Reduce the following
expression using Boolean Algebra laws
a. A’B’C’+ A’B’C + AB’C’ + ABC
b. [ (A+B)’ + C]’ (4)
ii.Realizethe given expression using only NAND gates and inverters XYZ + X’Y’Z’
(4)
iii.Design a full adder, constructs the truth table, simplify the output equations and draw
the logic diagram (8)
UNIT V
Communication Engineering
PART-A
1.What is communication ?
Transfer of information from one place to another is called communication.
2.What are the types of signals?
1.Analog signals
2.Digital signals
3.Give few examples of Analog signals?
1.Telephone signal
2.Radio broadcast signal
3.T.V singal
4. Define modulation? Modulation is the process of changing some parameters of a high frequency
carrier signal in according with the instantaneous variation of the message signal
5. What are the processes involved in analog to digital conversion?
1.Sampling
2.Quantization
3.Encoding
6.Write down few waveform coding technique.
1.PCM- Pulse code modulation
2.DCPH- Differential pulse code modulation
3.DM- Delta modulation
4.ADM- Adaptive delta modulation.
7. Based on the modulation index classify AM modulator’
1.Under modution
2.Critical modulation
3.Over modulation
8.Define angle modulation.
Angle modulation is the process by which the angle of the carrier signal is varied in accordance with the amplitude variation of the message signal
9.Define modulation lined in case of FH.
m=s/fm=maximum frequency deviation/modulation frequency
10.what is Radio communication?
Radio communication is transmission of speech,music,entertainment programmer.These informations are transmitted as radio waves.
11.Classify Radio receivers.
1.TRF-Tuned radio frequency receiver
2.SHR-Super heterodyne receiver.
12.What are the two types of T.V
1.Monochrome system
2.Color T.V system
13.What is facsimile?
In facsimile process the effective transmission and exact reproduction of still photographs,documents and other maps have to be done.
14.What is microwave? Electromagnetic waves in the frequency range of 1GHz to 50 GHz are
referred as microwaves.
15.List few advantages of microwave communication.
1.microwave communication offers wide bandwidth hence more number
of channels can be obtained.
2.Line of sight proropagation is move reliable when compared
to software communication.
3.Improved directivity with an aerial array.
4.Low power requirements in the order of milliwatts and microwaves.
16.List few applications of microwaves communication.
1.Terrestial microwave links are used to carry telephony,data and T.V
signals.
2.Satellite communication uses microwave frequencies for their oprerations.
3.microwave radiation has aiso found some medical applications for heatig
tumours.
4.Microwave can be used for material cutting.
17.Based on coverage classify the orbits.
Polar orbits
2.Inclined orbit
3.Equatorial orbit
PART B
1. (i) Show and discuss the block diagram of radio broadcasting and reception system and
explain the function of each block. (10)
(ii) Demonstrate on optical fiber communication (6)
2. (i)Illustrate the circuit diagram of balanced modulator and explain its operation. (8)
(ii) With a neat block diagram explain the principle of operation of FAX. (8)
3. Discuss any one method for suppressing the unwanted sideband. Support your answer with
the required diagrams. (16)
4. Summarize the principle of Amplitude & Frequency Modulation and its need. (16)
5. Conclude the usage of satellite for long distance communication with a neat block diagram
basic satellite transponder. (16)
6. Describe in detail with the necessary diagram the microwave and satellite communication
system. (16)
7. Explain in detail the functional diagram of Monochrome TV transmitter and receiver.
(16)
8. (i)Point out a Typical Television video signal, Explain how this is converted to image on TV
screen 10
(ii). A 10MHz sinusoidal carrier wave of amplitude 10mV is modulated by a 5KHz sinusoidal
audio signal wave of amplitude 6mV. Design and find the frequency components of the resultant